The present invention relates to a bearing-less connecting rod, and a method of producing a connecting rod The present invention also relates to an internal combustion engine, and an automotive vehicle including such a connecting rod.
The connecting rod is used for linking a crankshaft to a piston. The connecting rod includes a bar-like rod main body a small end which is provided at one end of the rod main body. A large end is provided at the other end of the rod main body. The thicker the connecting rod body, the higher the load can be applied to the con-rod during engine operation
The small end of the con rod contains a piston pin bore and allows a piston pin to extend through said bore. The small end is mechanically connected to a piston via the piston pin. Opposite the small end, the large end of the con rod contains a crankpin bore for allowing a crankshaft journal to extend through said bore. The big end is mechanically connected to a crankshaft.
In this invention embodiment, the big end is split into two pieces. The rod portion continues from one end of the rod main body. The cap portion is coupled to the rod portion with bolts. The connecting rod in this invention is referred to as a split-type connecting rod.
Requirements on the mechanical characteristics of a connecting rod differ from region to region. For example, the small end and rod main body of a connecting rod are required to have a high strength and a high toughness so as not to undergo fatigue failure or impact failure during use. The big end of the connecting rod is designed so diameter surface of the bore does not deform from the friction against the crankshaft journal.
If an alloy whose elastic modulus is lower than that of steel is used as the material of a connecting rod, weight reduction may be achieved, but the rigidity of the big end will be insufficient. Designing a connection rod to have a size for attaining sufficient rigidity will detract from the advantage of weight reduction.
Connecting rods transmit power generated during the combustion cycle from the piston to the crankshaft of the engine. Connecting rods are usually defined by a first end and a second end. The first end and the second end both typically include an aperture present on each end of the connecting rod. Typically, the aperture present in the first end of the connecting rod is smaller than the aperture present in the second end of the connecting rod. The aperture in the first end of the connecting rod is configured to connect to the piston by way of a piston pin. The aperture in the second end of the connecting rod is configured to connect to the crankshaft by way of a crankshaft pin.
Steel is the most common material used to manufacture connecting rods and crankshaft journals. The gap between the big end inner diameter and the crankshaft journal is very small. The gap size is on the order of 0.005 inches. The close tolerances between the inside bore of the con rod and the journal surface of the two components restricts the amount of engine oil present between the crankshaft bore and the journal.
Typically, a soft, and tough metallic bearing surface resides between the journal surface and the inner diameter of the large end bore. This soft metal surface reduces friction and provides some lubrication to the inner diameter and crankshaft journal. Traditionally, a copper-lead alloy is used for the bearing material. The relatively soft lead copper alloy provides lubrication, and eliminates most of the steel to steel contact that would cause seizing and engine failure.
The soft metal bearing combinations are susceptible to fatigue and failure. Metal bearings also increase the mass of the connecting rod assembly, and make the engine assembly process more complex.
The need for a connecting rod having a bearing-less large end capable of withstanding the high pressure exerted on the load bearing surface of the connecting rod is addressed in this invention. There is also need for a connecting rod that provides a cost-effective performance while remaining practical for production in a mass manufacturing environment.